Apparatus for forming a continuous curb structure

ABSTRACT

An apparatus for forming a continuous strip of pavement such as a curb, gutter or the like along a prepared ground surface. The apparatus is self-propelled and includes a mold adapted to continuously extrude a preformed paving strip as the apparatus moves along the ground. Provision is made for automatically adjusting the elevation of the mold according to an externally positioned control line, and for maintaining the opposite sides of the mold substantially level with respect to each other. Provision is also made for automatically controlling the direction of movement of the apparatus in accordance with the external control line.

United States Patent 1 1 Smith [111 3,749,504 [451 July 31,1973

[ APPARATUS FOR FORMING A CONTINUOUS CURB STRUCTURE [75] Inventor: RoyW. Smith, Salisbury, NC.

[73] Assignee: Power Curbers, Ine., Salisbury, NC.

[22] Filed: Apr. 30, 1971 [21] Appl. No.: 138,882

3,635,131 1/1972 Larsen 94/46 R 3,264,959 8/1966 Shea 94/46 AC 3,249,0265/1966 Curlett 94/46 AC 2,864,452 12/1958 Guntert 94/46 AC 3,540,36011/1970 Snow 94/46 AC Primary Examiner-Nile C. Byers, Jr.Attorney-Parrott, Bell, Seltzer, Park & Gibson [57 ABSTRACT An apparatusfor forming a continuous strip of pavement such as a curb, gutter or thelike along a prepared ground surface. The apparatus is self-propelledand includes a mold adapted to continuously extrude a preformed pavingstrip as the apparatus moves along the ground. Provision is made forautomatically adjusting the elevation of the mold according to anexternally positioned control line, and for maintaining the oppositesides of the mold substantially level with respect to each other.Provision is also made for automatically controlling the direction ofmovement of the apparatus in accordance with the external control line.

15 Claims, 8 Drawing Figures PATENIEU JUL 3 1 I973 SHEEI 1 OF 4PATENTEUJULIB 1 m5 3@ 749,504

SHEET 3 BF 4 Resaavm E,

mmguma 1 ms ,5 4

saw a DP 4 Qesrravonz,

. APPARATUS FOR FORMING A CONTINUOUS CURB STRUCTURE The presentinvention relates to an apparatus for extruding a preformed paving stripalong a ground surface. More specifically, the invention relates to anapparatus adapted to form a continuous and level concrete curb along aground surface, either before or after the roadbed has been laid, andwherein the apparatus is accurately guided along a predetermineddirection and at a predetermined elevation by an external control linepositioned adjacent the ground surface.

In recent years, several machines have been developed which are designedto continuously form highway curbs and the like without using manuallypositioned forms or rails. While such machines are an obviousimprovement over the previous manual construction methods, they have notproven satisfactory in all applications since they are generally smallin size and have a limited production capacity. In addition, mostmachines of this type have no provision for adjusting the position ofthe mold to counteract the effect of an uneven ground surface, and thusthey must rely on an accurately graded ground surface to obtain a levelcurb and one which is properly oriented with regard to the desiredelevation and direction. This procedure is obviously unsatisfactorysince conventional grading equipment is unable to provide the requiredaccuracy.

In one-known curb extrusion machine, an attempt has been made toovercome the difficulties resulting from an uneven ground surface byproviding an externally positioned control line and a follower attachedto the machine. By visually observing the position of the follower inrelation to the control line, the machine operator is able to detect adeviation from the predetermined elevation and direction. Upon observingsuch deviation, the operator then manually adjusts the orientation ofthe machine to effect corrective action. This procedure is alsounsatisfactory since an additional person is required to continuallyobserve the follower, and adjustment often occurs after a substantialdeviation has occurred.

Another known curb extrusion machine is driven by and supported upon twoendless steel trackways or belts, one on each side, which extendsubstantially the full length of the machine. Steering is accomplishedby varying the relative speed of the two tracks, but this produces afishtailing movement which can deform the extruded curb. In addition,the above machine is incapable of turning on a radius shorter than abouteighty feet, and thus it is unsuitable for many applications.

It is accordingly an object of the present invention to provide a curbforming machine which is adapted to continuously form a free standingconcrete-curb at a high rate of production and while utilizing a minimallabor force.

It is another object of the present invention to provide a curb formingmachine which automatically compensates for an uneven ground surface byautomatically maintaining the mold in a substantially level conditionfrom side to side, and at a predetermined elevation represented by anexternal control line. It is also an object to provide means foradjusting the leveling mechanism such that the machine may maintain asomewhat non-level condition and thereby conform to a tapered groundsurface.-

It is another object of the present invention to provide a curb formingmachine which automatically follows a predetermined direction, and whichis supported by an independent wheel member at each of the four cornersof the machine. In this connection, it is also an object of thisinvention to provide a steering mechanism adapted to turn the machineabout a relatively short radius and without deforming the extruded curb.

It is a further object of the present invention to provide a curbforming machine having an adjustable width whereby molds of various sizeand configuration may be selectively mounted within the frame of themachine.

These and other objects and advantages of the present invention areachieved in the embodiment illustrated herein by the provision of amachine which comprises a generally rectangular frame having asupporting wheel member positioned at each of the four corners. Each ofthe wheel members is adjustably interconnected to the frame such thateach wheel member may be selectively and independently raised or loweredwith respect thereto. Elevation sensor means is carried by the frame andis adapted to generate an output signal coordinated to a displacement ofthe frame above or below a pre-selected elevation represented by anexternal control line, and elevation control means is provided which isresponsive to the output signal from the elevation sensor means forraising or lowering selected ones of the wheel members to therebymaintain the elevation of the machine at a pro-selected elevation withrespect to the control line. Level sensor means is also carried by themachine and is adapted to generate an output signal coordinated to thedisplacement of one side of the machine from a level condition withrespect to the other side, and level control means is provided which isresponsive to an output signal from the level sensor means for raisingor lowering selected wheel members to reestablish a level conditionbetween the two sides. Direction sensor means may also be carried by theframe which is adapted to generate an output signal coordinated to adeviation in the direction of movement of the machine from that of theexternal control line, and direction control means is then provided tochange the direction of movement of the machine in accordance with theoutput signal from the direction sensor means.

Some of the objects of the invention having been stated, other objectswill appear as the description proceeds, when taken in connection withthe accompanying drawings, in which FIG. 1 is a perspective view of acurb forming apparatus embodying the features of the present invention;

FIG. 2 is a perspective view, partly sectioned, illustrating the rearend of the machine shown in FIG. 1 and the curb formed thereby;

FIG. 3 is a schematic plan view of the frame and stearing mechanism forthe above apparatus;

FIG. 4 is a schematic side view of the apparatus and illustrating thestructure for attaching the mold to the frame;

FIG. 5 is a schematic diagram of the drive mechanism for the aboveapparatus, with the wheels being laid apart for clarity of illustration;

FIG. 6 is a schematic diagram of the steering mechanism of the aboveapparatus;

FIG. 7 is a schematic diagram of the rear elevation and levelingcontrols for the above apparatus; and

FIG. 8 is a schematic diagram of the front elevation and levelingcontrols for the apparatus.

Referring more specifically to the drawings, the curb forming apparatusis indicated generally at and will be seen to include a generallyrectangular frame 12 having supporting wheel members I4, 15, 16 and 17at each of the four corners. More particularly, the wheel members 14 and15 are positioned at the front end of the apparatus, and the wheelmembers 16 and 17 are positioned at the rear end thereof. Also, thewheel members 14 and 16 define the near side of the apparatus and thewheel members 15 and I6 define the far side.

Each of the wheel members 14 17 comprises a frame 20 supporting avertical post 22, spaced sprockets 24 and 25 (FIG. 5) carrying theendless trackway 26, and a reversible hydraulic motor 28 adapted torotate the sprockets 24 and trackway to thereby propel the apparatus ineither direction. Each motor 28 includes a forward hydraulic port 280adapted to rotate the trackway in the forward direction, and a reverseport 28!) adapted to rotate the trackway in the reverse direction. Theposts 22 are each slidably received in a sleeve 30 which is fixedlycarried by the frame 12 of the apparatus, and means is provided foradjustably interconnecting the various posts within their respectivesleeves (and thus the wheels to the frame) such that each wheel may beindependently raised or lowered with respect to the frame. Thisinterconnecting means includes a vertically directed threaded stud 31rotatably carried within the sleeve 30 and an internally threaded member32 engaging the stud and fixedly carried by the post 22.

To concurrently power the hydraulic motors 28 and thereby propel thedevice in either direction, there is provided a hydraulic systemschematically illustrated in FIG. 5. As illustrated, the system includesa prime mover 33 which typically comprises an internal combustionengine, and a hydraulic pump 34 driven by the engine 33 and operativelyconnected to the reservoir 36. The pump 34 is adapted to deliverpressurized fluid to the manually operable fluid control valve 38. Aswill be apparent, the valve 38 has a neutral position (as shown) whereinno fluid is delivered to the wheel motors 28, a lowered position fordelivering the pressurized fluid through line 40 to the forward motorports 28a, and a raised position for delivering the fluid through line42 to the reverse motor ports 28b. Also, the pump 34 may include a speedcontrol lever 44 of conventional design. By this arrangement, theoperator of the apparatus may control the direction of movement of thedevice by actuating the valve 38, and may also vary the speed in eitherdirection by controlling the lever 44.

As best seen in FIGS. 3 and 4, the frame 12 comprises two generallyparallel side members 46 and 47 which are interconnected by a number oftransverse members 48. As is shown, the transverse members 48 areadjustable in length such that the lateral spacing of the side members46 and 47 may also be adjusted. If desired, a seat 50 and control panel51 may be secured to the rear transverse member 48 as seen in FIG. 4.

A mold 52 is carried centrally within the frame 12 and is adapted toreceive a paving material such as cement or asphalt and form the sameinto a continuous strip as the apparatus moves toward the right as seenin FIG. 4. More particularly, the mold 52 is removably connected to theframe 12 by a forward vertically adjustable connection 54 and a rearvertically adjustable connection 56. These connections permit verticaladjustment of the mold with respect to the frame, and also permit theremoval of the entire mold from the frame such that a mold of differentsize or configuration can be substituted therefor. Also, since theconnecting members 48 of the frame are adjustable in length, moldshaving different lateral dimensions may be selectively carried withinthe frame.

The mold 52 comprises an upper hopper portion 58 which is adapted toreceive a relatively large supply of the paving material from a deliverytruck or the like, and a lower rearwardly extending mold portion 60having an open bottom and an open rear end. The lower mold portion 60 isshaped to provide the desired configuration to the finished curb 62 asseen in FIG. 2. Also, a pair of conventional electrical vibrators 63extend into the hopper portion 58 and are adapted to compact and densifythe paving material in a manner well known in the art. The vibrators 63may be powered by an electrical generator 64 operatively connected tothe engine 33.

In order to automatically guide the apparatus along the prepared orgraded ground surface 65 as seen in FIGS. 1 and 2, there is provided anexternal control line 66 positioned adjacent the edge of the surface 65.For the reasons to become apparent, the line 66 should be accuratelypositioned in relation to the desired direction and elevation of thefinished curb 60.

The structure for maintaining the frame 12 and mold 52 at apredetermined elevation in relation to the control line 66 includeselevation sensor means comprising the front control line follower 68carried by the near side of the frame 12 adjacent the wheel member 14,and the rear control line follower 69 carried by the near side of theframe adjacent the wheel member 16. Thus the follower 68 is designed toregister the displacement of the front end of the apparatus (and thusthe front portion of the mold 50) above or below the desired elevation,and the rear follower 69 registers the displacement of the rear end ofthe apparatus (and thus rear end of the mold 50) from the desiredelevation.

Each of the control line followers 68 and 69 includes a horizontallydirected arm 72 which is adapted to contact the control line 66. The arm72 has a neutral position indicating that the frame and mold 50 are atthe proper elevation. In addition, the followers are adapted to generatean electrical output signal which is indicative of the direction ofdisplacement of the respective arm from its neutral position, and whichis also proportional to the extent of such displacement. Generally, thisis accomplished by means of a precision potentiometer which is rotatedeither up or down in response to movement of the arm 72. Wire followersof this type are well known to those skilled in the art and aremanufactured and sold for example by Moog, lnc., East Aurora, New York,under designation Model 86-117.

As indicated above, each of the wheel members is adjustablyinterconnected to the frame 12 by means of the stud 31 and threadedmember 32 such that each wheel member may be selectively raised orlowered with respect to the frame. To control the elevation of the wheelmembers, there is provided elevation control means which is responsiveto the output signals of the wire followers 68 and 69 to rotate selectedstuds to raise or lower selected wheels and thereby maintain the desiredelevation. Specifically, the elevation control means associated with thefront portion of the machine is shown schematically in FIG. 8. Thisfront elevation control means is responsive to the output signal fromthe follower 68 and is designed to raise or lower the wheel member 14 tothereby maintain the elevation of that portion of the frame 12 and moldadjacent the wheel member 14 at a preselected elevation in relation tothe elevation of the control line 66. The front elevation control meanscomprises a reversible hydraulic motor 75 operatively connected to thestud 31 associated with wheel member 14, the motor 75 having separateforward and reverse ports 75a and 75b respectively. Hydraulic pump meansis provided for selectively supplying pressurized hydraulic fluid tooneof the motor ports to thereby rotate the stud, and comprises thehydraulic pump 76 and flow control valve 78 positioned between the pump76 and ports of motor 75. The valve 78 is operatively connected throughan electrical transducer or converter 80 to the line follower 68. Theconverter 80 is conventional, and may for example comprise Model 82-254manufactured by Moog, Inc. The valve 78 is also conventional and may forexample comprise a four way sliding spool valve in which the outpfutflow is proportional to the electrical input current from the converter80. Moog, Inc. manufactures a valve of this type under the designationSeries 76.

The elevation control means associated with the rear portion of themachine and the rear follower 69 is shown in FIG. 7. The system isgenerally similar to that described above and comprises a reversiblehydraulic motor 82 connected to the stud of wheel member 16, a hydraulicpump 84 driven by the engine 33, and a separate flow control valve 86for selectively directing the pressurized fluid through one of the ports82a and 82b of motor 82. The valve 86 is connected to the follower 69via the converter 88 in a manner similar to the arrangement describedabove.

Level sensor means, comprising the front level sensor 90 carried by thefront end of the frame intermediate the wheel members 14 and and rearlevel sensor 92 carried by the rear end of the frame intermediate thewheel members 16 and 17, is provided for generating output signalscoordinated to a displacement of one side of the apparatus from a levelcondition with respect to the other side. Each of the level sensors areof similar construction, and generally comprise a dampened pendulum 94which is adapted to provide a gravity vertical reference defining aneutral or level position of the frame. In addition, the sensors 90 and92 include means for generating an electrical signal indicative of thedirection of pendulum displacement caused by a non-level condition, andwhich is also proportional to the extent of the angular displacementfrom its neutral position. Such sensors are commerically available andmay for example comprise Model 86-121 manufac" tured by Moog, Inc. Amanually controlled adjustment 96 may also be provided for each levelsensor which is adapted to vary the efi'ective neutral position of thependulum 94 and thereby permit the apparatus to maintain a preselectednon-level condition during movement along the ground surface. As will beapparent, this feature is desirable when it is desired to form the curbon a crowned or non-level ground surface. Thus in many cases it may bedesirable to place the curb squarely on a crowned surface even thoughthe curb itself may not be level from side to side.

To effect leveling of the apparatus upon a signal from the sensors and92, there is provided level control means for selectively actuating theinterconnecting means associated with the far side wheel members 15 and17. The level control means associated with the sensor 90 and frontwheel member 15 includes a reversible hydraulic motor 98 operativelyconnected to the stud and having separate forward and reverse ports 98aand 98b respectively. In addition, hydraulic pump means is providedwhich comprises the pump 76 and separate flow control valve 100 forselectively supplying pressurized hydraulic fluid to one of the ports ofmotor 98. A converter 101. similar to those described above ispositioned between the valve 100 and level sensor 90. The valve 100 ispreferably similar to those described above, and comprises a four-waysliding spool valve in which the output flow is proportional to theelectrical input current. Thus, the power delivered to the motor 98 isproportional to the extent of displacement of the pendulum 94 of sensor90.

The level control means associated with the rear portion of the machineand sensor 92 is shown in FIG. 7 and will be seen to be generallysimilar to that described above with respect to the sensor 90.Specifically, the rear level control means comprises the hydraulic motor102 connected to the stud of wheel member 17, and the hydraulic pumpmeans includes the hydraulic pump 84, and the four-way valve 104. Aconverter 106 is similarly positioned between the valve 104 and sensor92.

As best seen in FIGS. 1 and 6, direction sensor means is carried by theframe for generating an output signal coordinated to a deviation in thedirection of movement of the apparatus from a predetermined directioncorresponding to that of the control line 66. Such direction sensormeans comprises a line follower 108 similar in construction to thefollowers 68 and 69 but wherein the control arm 109 is verticallydirected for lateral movement. Direction control means is provided whichis responsive to the output signal from the line follower 108 toselectively change the direction of the front pair of wheels and therebycause the apparatus to turn and re-establish its predetermineddirection. Specifically, the direction control means comprises the post22 and sleeve 30 mounting interconnections associated with the frontpair of wheel members 14 and 15 wherein such wheels are each rotatableabout the vertical axis corresponding to the axis of its post andsleeve. A tie rod 110 operatively connects the front pair of wheels toprovide for concurrent rotation about these axes, and hydraulic means isprovided for rotating the front wheels about their respective axes. Suchhydraulic means comprises the cylinders 112 and 114 carried by the frame12, a piston 1 15 slidably carried in the cylinder 112 and operativelyconnected to the post 22 of wheel member 15, and a piston 117 slidablycarried in the cylinder 114 and operatively connected to the post 22 ofwheel member 14. Each cylinder includes a front port 1120 and 1140respectively on one side of the piston, and a rear port 1 12b and 1 14bon the opposite side thereof. A hydraulic pump 120 and flow controlvalve 122 are provided for selectively supplying pressurized hydraulicfluid through line 122 to ports 1l2b and 1140, or through line 123 toports 114k and 112a. By this arrangement, the pistons may be translatedin opposite directions within their respective cylinders to concurrentlyrotate the wheel members 14 and 15 about a pair of vertical axes definedby the post and sleeve of each wheel, The flow control valve 122 issimilar in construction to the above described four-way sliding spoolvalves wherein the output flow is proportional to the electrical input,and a converter 125 as described above is interposed between the valve122 and sensor 108.

It is believed that the operation of the apparatus 10 will be apparentfrom the above description. Generally, however, that the apparatus ispropelled along the ground surface 65 by the engine 33 acting throughpump 34 and valve 38 to the wheel motors 28. The speed may be accuratelycontrolled in either the forward or reverse directions by the controllever 44, and it will be apparent that the apparatus is able to climb arelatively steep grade by reason of the traction developed by thefour-wheel drive arrangement.

If the apparatus rises above the predetermined elevation, either one orboth of the sensors 68 and 69 will register the deviation and signaleither one or both of the motors 75 and 82 to appropriately adjust theelevation of the wheel members and 16. Such movement by these wheelswill undoubtedly cause the far side to become non-level with respect tothe near side, which in turn will result in one or both of the sensors90 and Q2 taking corrective action by actuating either one or both ofthe motors 98 and 102. While duplicate elevation and leveling controlsystems (i.e. front and rear) have been illustrated herein, it will beapparent that in many applications a single system will be adequate,particularly where the apparatus has a relatively short length. However,when the apparatus is large and the mold 52 has a relatively longlength, the illustrated duplicate system is preferable.

Should the apparatus deviate from its designated direction of movement,the sensor 108 will actuate the valve 122 to rotate the front wheelmembers in the appropriate direction. Since rotation occurs about avertical axis extending upwardly from each front wheel member, it willbe appreciated that the entire device may be turned about a relativelyshort radius, which in actual practice may be as short as feet. Also, itis apparent that there will be no significant fishtailing at the rearportion of the machine and thus there will be no deformation of theextruded curb.

In the drawings and specification, there has been set forth a preferredembodiment of the invention, and although specific terms are employed,they are used in a generic and descriptive sense only and not forpurposes of limitation.

That which is claimed:

l. A self-propelled apparatus for forming a continuous strip of pavingmaterial such as a curb, gutter, or the like along a prepared groundsurface having an external control line, said apparatus comprising agenerally rectangular frame defining a front end, a

rear end, a near side, a far side, and four corners,

a supporting wheel member positioned at each of the four corners of theframe, means for adjustably interconnecting the supporting wheel membersand frame such that each of the wheel members may be selectively andindependently raised or lowered with respect to the frame,

power means carried by said frame for rotating at least two wheelmembers to propel the apparatus along the ground surface,

mold means carried centrally within said frame for receiving the pavingmaterial and forming the same into a continuous strip as the apparatusmoves along the ground surface,

elevation sensor means including a first control line follower carriedby the near side of said frame adjacent one near side wheel member forgenerating an output signal proportional to a displacement of thatportion of the frame and mold means adjacent said one near side wheelmember above or below a preselected elevation represented by theexternal control line, and a second control line follower carried by thenear side of said frame adjacent the other near side wheel member forgenerating an output signal proportional to a displacement of thatportion of the frame and mold means adjacent said other near side wheelmember above or below a preselected elevation represented by theexternal control line,

first elevation control means carried by said frame and responsive tothe output signal from said first control line follower for selectivelyactuating said interconnecting means associated with said one near sidewheel member to selectively raise or lower such wheel and therebymaintain the elevation of that portion of the frame and mold meansadjacent said one near side wheel member at a preselected elevation inrelation to the elevation of the control line,

second elevation control means carried by said frame and responsive tothe output signal from said second control line follower for selectivelyactuating said interconnecting means associated with said other nearside wheel member to selectively raise or lower such wheel and therebymaintain the elevation of that portion of the frame and mold meansadjacent said other near side wheel member at a preselected elevation inrelation to the elevation of the control line,

level sensor means including a first level sensor carried by the frameadjacent said one near side wheel member for generating an output signalproportional to a displacement of the far side of the apparatus from alevel condition with respect to the near side and a second level sensorcarried by the frame adjacent said other near side wheel member forgenerating an output signal proportional to the displacement of the farside of the apparatus from a level condition with respect to the nearside,

first level control means carried by said frame and responsive to theoutput signal from said first level sensor for selectively actuatingsaid interconnecting means associated with the far side wheel memberopposite said one near side wheel member to raise or lower such far sidewheel member to reestablish a level condition between the two sides, and

second level control means carried by said frame and responsive to theoutput signal from said second level sensor for selectively actuatingsaid intercom necting means associated with the far side wheel memberopposite said other near side wheel member to raise or lower such farside wheel member to re-establish a level condition between the twosides,

whereby said first and second level sensors act independently from eachother to provide accurate control of the elevation of the far side ofthe apparatus with respect to that of the near side.

2. The apparatus as defined in claim 1 wherein said means for adjustablyinterconnecting each of the wheel members and frame includes avertically directed externally threaded stud rotatably carried by one ofeither the wheel member or frame, and an internally threaded memberengaging said stud and fixedly carried by the other of either the wheelmember or frame, such that rotation of said stud vertically translatesthe wheel in relation to said frame.

3. The apparatus as defined in claim 2 wherein each of said first andsecond control line followers comprises a horizontally directed armadapted to contact the control line and having a preselected neutralposition, and means for generating an electrical signal indicative ofthe direction of displacement of the arm from its neutral position andwhich is also proportional to the extent of such displacement.

4. The apparatus as defined in claim 3 wherein each of said first andsecond level sensors comprises a dampened pendulum adapted to provide agravity vertical reference defining a neutral position relative to saidframe, and means for generating an electrical signal indicative of thedirection of displacement of the pendulum from said neutral position andwhich is proportional to the extent of such displacement.

5. The apparatus as defined in claim 4 wherein each of said first andsecond elevation control means and each of said first and second levelcontrol means includes a reversible hydraulic motor operativelyconnected to the associated stud and having separate forward and reverseports.

6. The apparatus as defined in claim 5 further comprising firsthydraulic pump means carried by said frame for selectively supplyingpressurized fluid to the motor ports of said first elevation controlmeans and said first level control means, said first hydraulic pumpmeans comprising a first hydraulic pump, a first flow control valvepositioned between said first hydraulic pump and the motor ports of saidfirst elevation control means, and a second flow control valvepositioned between said first hydraulic pump and the motor ports of saidfirst level control means, each of said first and second valvesincluding means for selectively directing the pressurized fluid throughone of the motor ports at a rate proportional to the signal from theassociated sensor means.

7. The apparatus as defined in claim 6 further comprising secondhydraulic pump means carried by said frame for selectively supplyingpressurized fluid to the motor ports of said second elevation controlmeans and said second level control means, said second hydraulic pumpmeans comprising a second hydraulic pump, a third flow control valvepositioned between said second hydraulic pump and the motor ports ofsaid second elevation control means, and a fourth flow control valvepositioned between said second hydraulic pump and the motor ports ofsaid second level control means, each of said third and fourth valvesincluding means for selectively directing the pressurized fluid throughone of the motor ports at a rate proportional to the signal from theassociated sensor means.

8. The apparatus as defined in claim 4 wherein each of said first andsecond level'sensors further comprises manually controlled adjustmentmeans for varying the neutral position of said pendulum to therebypermit the apparatus to maintain a preselected non-level conditionduring movement along the ground surface.

9. The apparatus as defined in claim 1 further including directionsensor means carried by said frame for generating an output signalcoordinated to a deviation in the direction of movement of the apparatusfrom a predetermined direction corresponding to the direction of theexternal control line, and

direction control means responsive to the output signal from saiddirection sensor means for selectively changing the direction of onepair of end wheel members to cause the apparatus to turn and reestablishthe predetermined direction.

10. The apparatus as defined in claim 9 wherein said direction sensormeans comprises a control line follower having a vertically directed armadapted to contact the control line and having a preselected neutralposition, and means for generating an electrical signal indicative ofthe direction of displacement of the arm from its neutral position andwhich is proportional to the extent of such displacement.

1 l. The apparatus as defined in claim 10 wherein said direction controlmeans comprises means mounting the front end pair of wheel members forrotation about a pair of vertical axes with one of said axes extendingupwardly from each wheel member, a tie rod operatively connecting saidfront end pair of wheel members to provide concurrent rotation of thewheel members about said axes, and steering hydraulic means for rotatingsaid wheel members about their respective axes.

12. The apparatus as defined in claim 1 1 wherein said steeringhydraulic means comprises a hydraulic cylinder carried by said frame andhaving separate forward and reverse ports, a piston carried in saidcylinder and operatively connected to said wheel member mounting means,and hydraulic pump means for supplying pressurized hydraulic fluid tosaid cylinder ports and including a hydraulic pump and a flow controlvalve positioned between said hydraulic pump and said hydrauliccylinder, said flow control valve including means for selectivelydirecting the pressurized fluid through one of said cylinder ports at arate proportional to the signal from said direction sensor means.

13. The apparatus as defined in claim 1 wherein said power meansincludes a reversible hydraulic motor operatively connected to eachwheel member, each of said motors including separate forward and reverseports, and hydraulic pump means for concurrently supplying pressurizedhydraulic fluid to either the forward or reverse ports of all of saidmotors and including a hydraulic pump and a manually operated flowcontrol valve interposed between said hydraulic pump and motors.

14. The apparatus as defined in claim 1 wherein said mold meanscomprises an upper hopper portion adapted to receive the pavingmaterial, and a lower mold portion having an open bottom and open rearend.

15. The apparatus as defined in claim 14 wherein said mold means furthercomprises vibrating means for compacting and densifying the pavingmaterial received therein.

1. A self-propelled apparatus for forming a continuous strip of pavingmaterial such as a curb, gutter, or the like along a prepared groundsurface having an external control line, said apparatus comprising agenerally rectangular frame defining a front end, a rear end, a nearside, a far side, and four corners, a supporting wheel member positionedat each of the four corners of the frame, means for adjustablyinterconnecting the supporting wheel members and frame such that each ofthe wheel members may be selectively and independently raised or loweredwith respect to the frame, power means carried by said frame forrotating at least two wheel members to propel the apparatus along theground surface, mold means carried centrally within said frame forreceiving the paving material and forming the same into a continuousstrip as the apparatus moves along the ground surface, elevation sensormeans including a first control line follower carried by the near sideof said frame adjacent one near side wheel member for generating anoutput signal proportional to a displacement of that portion of theframe and mold means adjacent said one near side wheel member above orbelow a preselected elevation represented by the external control line,and a second control line follower carried by the near side of saidframe adjacent the other near side wheel member for generating an outputsignal proportional to a displacement of that portion of the frame andmold means adjacent said other near side wheel member above or below apreselected elevation represented by the external control line, firstelevation control means carried by said frame and responsive to theoutput signal from said first control line follower for selectivelyactuating said interconnecting means associated with said one near sidewheel member to selectively raise or lower such wheel and therebymaintain the elevation of that portion of the frame and mold meansadjacent said one near side wheel member at a preselected elevation inrelation to the elevation of the control line, second elevation controlmeans carried by said frame and responsive to the output signal fromsaid second control line follower for selectively actuating saidinterconnecting means associated with said other near side wheel memberto selectively raise or lower such wheel and thereby maintain theelevation of that portion of the frame and mold means adjacent saidother near side wheel member at a preselected elevation in relation tothe elevation of the control line, level sensor means including a firstlevel sensor carried by the frame adjacent said one near side wheelmember for generating an output signal proportional to a displacement ofthe far side of the apparatus from a level condition with respect to thenear side and a second level sensor carried by the frame adjacent saidother near side wheel member for generating an output signalproportional to the displacement of the far side of the apparatus from alevel condition with respect to the near side, first level control meanscarried by said frame and responsive to the output signal from saidfirst level sensor for selectiVely actuating said interconnecting meansassociated with the far side wheel member opposite said one near sidewheel member to raise or lower such far side wheel member tore-establish a level condition between the two sides, and second levelcontrol means carried by said frame and responsive to the output signalfrom said second level sensor for selectively actuating saidinterconnecting means associated with the far side wheel member oppositesaid other near side wheel member to raise or lower such far side wheelmember to re-establish a level condition between the two sides, wherebysaid first and second level sensors act independently from each other toprovide accurate control of the elevation of the far side of theapparatus with respect to that of the near side.
 2. The apparatus asdefined in claim 1 wherein said means for adjustably interconnectingeach of the wheel members and frame includes a vertically directedexternally threaded stud rotatably carried by one of either the wheelmember or frame, and an internally threaded member engaging said studand fixedly carried by the other of either the wheel member or frame,such that rotation of said stud vertically translates the wheel inrelation to said frame.
 3. The apparatus as defined in claim 2 whereineach of said first and second control line followers comprises ahorizontally directed arm adapted to contact the control line and havinga preselected neutral position, and means for generating an electricalsignal indicative of the direction of displacement of the arm from itsneutral position and which is also proportional to the extent of suchdisplacement.
 4. The apparatus as defined in claim 3 wherein each ofsaid first and second level sensors comprises a dampened pendulumadapted to provide a gravity vertical reference defining a neutralposition relative to said frame, and means for generating an electricalsignal indicative of the direction of displacement of the pendulum fromsaid neutral position and which is proportional to the extent of suchdisplacement.
 5. The apparatus as defined in claim 4 wherein each ofsaid first and second elevation control means and each of said first andsecond level control means includes a reversible hydraulic motoroperatively connected to the associated stud and having separate forwardand reverse ports.
 6. The apparatus as defined in claim 5 furthercomprising first hydraulic pump means carried by said frame forselectively supplying pressurized fluid to the motor ports of said firstelevation control means and said first level control means, said firsthydraulic pump means comprising a first hydraulic pump, a first flowcontrol valve positioned between said first hydraulic pump and the motorports of said first elevation control means, and a second flow controlvalve positioned between said first hydraulic pump and the motor portsof said first level control means, each of said first and second valvesincluding means for selectively directing the pressurized fluid throughone of the motor ports at a rate proportional to the signal from theassociated sensor means.
 7. The apparatus as defined in claim 6 furthercomprising second hydraulic pump means carried by said frame forselectively supplying pressurized fluid to the motor ports of saidsecond elevation control means and said second level control means, saidsecond hydraulic pump means comprising a second hydraulic pump, a thirdflow control valve positioned between said second hydraulic pump and themotor ports of said second elevation control means, and a fourth flowcontrol valve positioned between said second hydraulic pump and themotor ports of said second level control means, each of said third andfourth valves including means for selectively directing the pressurizedfluid through one of the motor ports at a rate proportional to thesignal from the associated sensor means.
 8. The apparatus as defined inclaim 4 wherein each of said first and second level sensors furthercompriSes manually controlled adjustment means for varying the neutralposition of said pendulum to thereby permit the apparatus to maintain apreselected non-level condition during movement along the groundsurface.
 9. The apparatus as defined in claim 1 further includingdirection sensor means carried by said frame for generating an outputsignal coordinated to a deviation in the direction of movement of theapparatus from a predetermined direction corresponding to the directionof the external control line, and direction control means responsive tothe output signal from said direction sensor means for selectivelychanging the direction of one pair of end wheel members to cause theapparatus to turn and re-establish the predetermined direction.
 10. Theapparatus as defined in claim 9 wherein said direction sensor meanscomprises a control line follower having a vertically directed armadapted to contact the control line and having a preselected neutralposition, and means for generating an electrical signal indicative ofthe direction of displacement of the arm from its neutral position andwhich is proportional to the extent of such displacement.
 11. Theapparatus as defined in claim 10 wherein said direction control meanscomprises means mounting the front end pair of wheel members forrotation about a pair of vertical axes with one of said axes extendingupwardly from each wheel member, a tie rod operatively connecting saidfront end pair of wheel members to provide concurrent rotation of thewheel members about said axes, and steering hydraulic means for rotatingsaid wheel members about their respective axes.
 12. The apparatus asdefined in claim 11 wherein said steering hydraulic means comprises ahydraulic cylinder carried by said frame and having separate forward andreverse ports, a piston carried in said cylinder and operativelyconnected to said wheel member mounting means, and hydraulic pump meansfor supplying pressurized hydraulic fluid to said cylinder ports andincluding a hydraulic pump and a flow control valve positioned betweensaid hydraulic pump and said hydraulic cylinder, said flow control valveincluding means for selectively directing the pressurized fluid throughone of said cylinder ports at a rate proportional to the signal fromsaid direction sensor means.
 13. The apparatus as defined in claim 1wherein said power means includes a reversible hydraulic motoroperatively connected to each wheel member, each of said motorsincluding separate forward and reverse ports, and hydraulic pump meansfor concurrently supplying pressurized hydraulic fluid to either theforward or reverse ports of all of said motors and including a hydraulicpump and a manually operated flow control valve interposed between saidhydraulic pump and motors.
 14. The apparatus as defined in claim 1wherein said mold means comprises an upper hopper portion adapted toreceive the paving material, and a lower mold portion having an openbottom and open rear end.
 15. The apparatus as defined in claim 14wherein said mold means further comprises vibrating means for compactingand densifying the paving material received therein.